In a small saucepan, combine maple syrup, bourbon, fresh orange juice, Dijon mustard, and whole grain mustard (if using). Bring to a boil over medium heat, then reduce to low and simmer for 5-10 minutes until glaze thickens.

Pour 1 cup of water into the bottom of your slow cooker. Place the spiral sliced ham cut side up in the slow cooker.

Carefully pour the prepared maple glaze over the ham, ensuring it drizzles into the crevices between the slices.

Cover the slow cooker and set on low heat. Cook for approximately 2.5 to 3 hours until it reaches an internal temperature of 140°F, basting with glaze once or twice.

For a sticky finish, transfer the ham to a baking dish, brush with reserved glaze, and broil for 3-5 minutes.